The present invention relates to a piston for fluid machines such as compressors that compress refrigerant gas for air-conditioning vehicles.
Japanese Unexamined Patent Publication No. 5-99146 describes a compressor piston 112 illustrated in the present specification at FIG. 6, which replicates the figure shown in the abstract of the Japanese reference and adds a leading one (1) digit to the reference numerals for parts described herein. As shown in FIG. 6 of the present specification, the resin piston body 130 is compression-molded to and joined to a metal coupler 120, to which a piston rod 113 is coupled. Since most of the piston 112 is made of resin, the piston 112 is relatively light. The light piston reduces inertia when the piston 112 reciprocates. As a result, power losses of the compressor are reduced.
However, in the publication, the piston body 130 is made of fluororesin such as polytetrafluoroethylene, which is a thermoplastic resin. Since such thermoplastic resin has poor adhesion to metal, the coupler cannot be joined to the piston with desirable strength.
In a typical compressor, rotation of a swash plate is converted into piston reciprocation through shoes. Each piston includes a body and a coupler, which are joined. Each piston is coupled to the swash plate through the shoes, which are retained in the coupler to slide freely.
In the typical compressor, force is applied to each piston through the shoes and the coupler by the swash plate. This causes frictional resistance between each piston and the wall of the corresponding cylinder bore. Accordingly, a torsional force is applied to the interface between each piston body and coupler. As a result, the metal couplers may be detached from the piston bodies, which are made of thermoplastic resin. This hinders smooth reciprocation of the pistons and damages the seal between the pistons and the cylinder bores.
An objective of the present invention is to provide a piston for fluid machines that allows the piston body to be firmly connected to the coupler.
To achieve the above objective, the present invention provides a piston for cooperating with a driving body in a machine. The piston comprises a metal coupler connected to the driving body. A body is made of thermosetting resin. The body is molded to the coupler.
Other aspects and advantages of the invention will become apparent from the following description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention.